I just started doing some serious trading with the new tools, and I'm confused. I'm seeing things in the market where the demand over is 300, but these items are not flagged as "high demand". However, other items with a demand of 60 is considered high demand. Is this bugged? I've been using the filter for high supply / demand, only to find out that I'm missing some of the best deals because things seem improperly marked. Would a sales manager please report to cash register B!

Oh, and how is it I can sell things to the market where there is zero demand and yet still make a profit against the galactic average?

I just started doing some serious trading with the new tools, and I'm confused. I'm seeing things in the market where the demand over is 300, but these items are not flagged as "high demand". However, other items with a demand of 60 is considered high demand. Is this bugged? I've been using the filter for high supply / demand, only to find out that I'm missing some of the best deals because things seem improperly marked. Would a sales manager please report to cash register B!

High demand is relative to the total demand for the product, and the (fairly small) effect of the demand curve on pricing depends on the relative amount not the absolute amount.

So, for example, Copper gets used in everything, and has a total demand of around 300t per economic unit [1]. Progenitor Cells, on the other hand, you only need a few grams per treatment, so a tonne of them lasts for ages [2], and the demand is around 0.3t per economic unit.

So an Industrial market with 100 economic units of size would have an expected peak demand of around 30,000t of Copper and 30t of Progenitor Cells. If some of this demand had been met, and the remaining market had a demand for 15,000t of Copper and 28t of Progenitor Cells, this would be high demand of Cells (28/30) but only medium demand for Copper (15000/30000)

[1] As a first approximation true of most stations, a market has economic units equal to the square root of its population.
[2] Unless you happen to be a techno-undead creature thought destroyed in an explosion but kept alive solely by vast quantities of them. Ahem.

Long story short, I was using the 'High Supply / Demand' filter to determine what bulk deliveries I should be making to the station during my next trip, yet the best sales (both in terms of immediate demand and profit margin) are hidden when I use this filter, making said filter useless to me. There's a column labeled "Demand" that has a very big number in it, yet this is not considered "High" compared to another number when it comes to the little green icon and filter. Surely my confusion is justified!

And speaking of zero demand, what does it mean when that number / graph icon turns red?

I'm doing BGS stuff which requires me to sell in a specific station, so that otherwise useful chart does me no good*. Now if BGS worked in reverse (reward me for buying at target station and then selling for a profit wherever I want), then that would make way more sense to me and I'd use that chart like you do. Unfortunately this is not to be, so I've got to play the BGS cards I've been dealt.

* Nevermind! I made a noob mistake regarding that little chart. I'm still waiting for a bit more light on the subject of the OP (I appreciate the answers but I'm still confused).

High demand is relative to the total demand for the product, and the (fairly small) effect of the demand curve on pricing depends on the relative amount not the absolute amount.

So, for example, Copper gets used in everything, and has a total demand of around 300t per economic unit [1]. Progenitor Cells, on the other hand, you only need a few grams per treatment, so a tonne of them lasts for ages [2], and the demand is around 0.3t per economic unit.

So an Industrial market with 100 economic units of size would have an expected peak demand of around 30,000t of Copper and 30t of Progenitor Cells. If some of this demand had been met, and the remaining market had a demand for 15,000t of Copper and 28t of Progenitor Cells, this would be high demand of Cells (28/30) but only medium demand for Copper (15000/30000)

[1] As a first approximation true of most stations, a market has economic units equal to the square root of its population.
[2] Unless you happen to be a techno-undead creature thought destroyed in an explosion but kept alive solely by vast quantities of them. Ahem.

The market average assumes BGS state "None" and in that state most goods will make a loss at 0 demand especially if bought from a market at low supply.

If the price is boosted by BGS states then it can end up way over the galactic average even at zero demand.

(I'd rather the demand curve was the big effect and the BGS states were the fine-tuning, rather than the other way round, but that's how it is)